When the cake has cooled, carefully slice in half horizontally with a serrated knife.

Sandwich the two cake layers with some of the chocolate buttercream icing, then spread the rest evenly around the outside and top of the cake.

Take a handful of the chocolate chips and carefully but firmly press them into the side of the cake. There will be some that fall off, but you can just pick these up and press them again. Continue this until the sides are all covered.

Cover the top of the cake with Maltesers, crushed biscuits and the mini marshmallows.

Heat the chopped chocolate and cream in the microwave for 30-second intervals, stirring in between, until melted.

Drizzle the melted chocolate over the top and down the sides. Make sure there is plenty dripping down from the edges!